So... lets start playing !
Since I want this to run for at least 2 years, I'm hoping to get a system that will either run everything I want it to during that time frame from its stock settings, or have the option for overclocking when the time comes. I know nothing about hardware so please help.

From what I read, most would go with the i5 2500k which seems to fit my needs, but what else ? It seems 8GB RAM is way enough (but memory ain't too pricey so maybe 16GB and be done with it for 3+ years ?), but which one should I take (PNY, Corsair, Kingston, G.SKills, etc.) and at what speed (1333 seem cheaper, but would 1600 be better for the future?) and then obviously, there's the whole compatibility problem... I'd give you guys a "prepared list", but everytime I try to make one I just select stuff almost randomly since I know nothing :/

Reading what you want to play at high to ultra @ 40fps and $1000 budget your aiming a bit low id say. I will admit my current build A to Z was roughly $1300 give or take a few bucks. However if your wanting only 40 fps im assuming your not even entertaining the thought of sli or cfx so budget could get closer to $900-1000 for basically 60fps maybe dumping to 50, lowest ive seen which was day of my build , 48fps full ultra in 25m raid being seeds exploding on rag. Thats not even a tickle to your eyes when raiding.

Now these are basics to get you looking at stuff more involved yourself. The rough area estimate is like $650 for those parts. This give's you some directions and some leeway to play w/ customizing it just to your liking. Lil research and a little direction is all it takes.

honestly, I would put off buying that heatsink for a few months or a year+ and just not OC... put that money into the Caviar Black. You can always buy backup storage when the price goes back down... but you want a good boot drive/load drive for your games. Also... that Video card is a bit crazy for what the OP is looking for... could stick with the 560 ti normal model and pick up the OS with his savings if he needs one.

noticed your in canada so id recommend checking out ncix.com. i bought a 2500k+gigabyte z68 mobo deal there a few weeks back for 389$, they have weekly sales in the top left hand side of their website and some of them are very good.Although your expactations are not very high with 40fps on ultra,this should be easy to do with a $1000 budget. i think i paid 370ish for a 750w xfx psu and 6950 gppu deal aswell, if you can find these deals there still,or similar thats about $800 leaving you with $200 for memory and a case. coolermaster haf 912 is around $50 and has alot of fans/fan mountings plus enough room for the 6950 and then do whatever you want for memory. I never drop below 70-80 fps with everything maxed on this set up even in a raid and at times i get near 200fps. BF3 maxed i run about 70fps. I have my chip overclocked a lil aswell and another thing you will def need is cooling for the chip, the crap the 2500k comes with is terrible so pick up a good noctua fan

Ty for everything guys ! I'll compile all that and make a "pre-build" I'll run by you again in case of compatibility issues!

To clarify, I currently play WoW at 20 FPS with everything at Low/Off and don't feel it's lagging... but just not very pretty!
I don't see how 60+ FPS would make it so amazing to the eye as I feel everything runs smooth at 20 FPS.

With your monitor at 1600x900, you could pay $500 and get everything you're asking for, going all the way up to $1000 on the same monitor would be a huge waste; I recommend grabbing a new monitor somewhere in that $1000 so you can game at 1920x1080 and appreciate your new hardware a little bit better.

If you're not doing it right now, you could save a pretty penny by downgrading to a H67 board and a normal i5 2500. Ivy Bridge is coming out soon, and most 1155 boards will be compatible. Instead of overclocking way down the line when Ivy Bridge is released, you can take the money you saved and put it towards a new processor or a new GPU (now or in the future, like a 6950).